If this is your first visit, be sure to
check out the FAQ by clicking the
link above. You may have to register
before you can post: click the register link above to proceed. To start viewing messages,
select the forum that you want to visit from the selection below.
The N75 has a circuit from 'wastegate control pressure' port to 'ambient' when not energized.
Unless there is a one way valve in there, when the MBC opens, pressure will short circuit back through the N75 rather than pushing the wastegate open.
You will also get bleed back through the MBC bleed port when the N75 fires. this will be les of an issue as the MBC bleed port should be small.
Whilst the engine is running the N75 is always operating and bleeding pressure off (unless its mapped differently to standard) but in this setup it's about getting the bleed setup and balanced with the MBC. To keep the N75 as the main control set the MBC to open between the maps max desired pressure and the map SVBL.
Good call Reg - A couple of one way valves might be required as it depends on the quality of the components, the spread of pressure settings & the efficiency of the N75.
Runs good on my AJT and the MBC is there simply to give the turbo/engine a little backup if the N75 fails to bleed enough pressure off at full chat.
If I could locate the voltage map for the N75 I'd look at upgrading it or possibly modifying the existing one.
Obviously VNT and vacuum operated turbos are another topic.
Runs good on my AJT and the MBC is there simply to give the turbo/engine a little backup if the N75 fails to bleed enough pressure off at full chat.
If I could locate the voltage map for the N75 I'd look at upgrading it or possibly modifying the existing one.
Obviously VNT and vacuum operated turbos are another topic.
I hope that's just a phrase you've used - the N75 doesn't bleed off anything - it opens the wastegate. There's very low flow rate through the N75, it's more than up to the job.
For bread and butter protection you could fit a BOV type additional wastegate.
Isn't the N75 map easy to find then? I thought it was quite a common mod to adjust it to drive VNTs.
I built a VNT controller for my old Golf on a PIC, it got more and more functionality and unknowingly I'd practically built half an ECU by the end. Gave up in the end because the servo couldn't keep up with rate of boost build - I just locked the vanes fully closed. At 35 psi the MAP became a bit of an issue for the valves and lifters Went quite well though.
Comment